Online Colour Selector

That firs - Color blender is qute and seems to be useful. The source code can be copied and I guess embeded on your site, so you can have the whole program there.

I've found a Color Picker 1.02. You put Mouse Over any color on the screen in Windows 95 - XP environment and you can catch a hex, RGB or RGB hex code and save it in clipboard with a click.
Free.